Method and composition for coating mat and articles produced therewith

ABSTRACT

A coated glass mat comprises a glass mat substrate having non-woven glass fibers and a coating which essentially uniformly penetrates the glass mat substrate to desired fractional thickness of the coated glass mat. The coating imparts a tensile strength to the coated glass mat which on average is at least 1.33 times greater than the tensile strength of the glass mat substrate without the coating. In example embodiments, penetration of the coating into the glass mat substrate preferably extends to a depth of from twenty five percent of a thickness of the coated glass mat to seventy five percent of the thickness of the coated glass mat. Moreover, a non-coated thickness of the coated glass mat is sufficiently thick for bonding purposes with, e.g., a gypsum slurry or other core materials such as thermoplastic or thermosetting plastics. The coating has a porosity in a range of from 1.3 CFM to 5.0 CFM, e.g., the coating comprises a coating blend which provides the coated glass mat with a porosity sufficient to allow water vapor to escape from a gypsum slurry when heated. The coating is preferably a coating blend comprised of water, latex binder, inorganic pigment, and inorganic binder.

This application is a continuation of U.S. patent application Ser. No.10/324,109 filed Dec. 20, 2002, entitled “METHOD AND COMPOSITION FORCOATING MAT AND ARTICLES PRODUCED THEREWITH”, which issued as U.S. Pat.No. 7,138,346, which claims the priority and benefit of U.S. ProvisionalApplication Ser. No. 60/341,277, filed Dec. 20, 2001, entitled “METHODAND COMPOSITION FOR COATING MAT AND ARTICLES PRODUCED THEREWITH”, eachof which are incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The field of the invention pertains to mats, webs, or facers for thebuilding construction industry, such as gypsum board fiberglass facersand thermosetting polyiso foam insulation board facers, as well asprocesses for making/applying such facers and products utilizing suchfacers.

2. Related Art and Other Considerations

Many forms of weather resistant webbed sheets have been developed forthe building construction industry for installation as an “underlayment”under shingles or under siding. Examples of such webbed sheets, alsocalled “construction paper”, range from the old original “tar paper”, upto the spun-bonded polyolefin house wraps of the present day.

Various types of webbed sheets have also been used as a “facer” materialfor foamed insulation board laminates, with the laminates ultimatelybeing utilized as side-wall or roofing insulation. For example, twofacers for a laminate board typically sandwich a core materialtherebetween, e.g., a laminated foam core, for example. A popularmaterial (“facer”) in this category is the web of U.S. Pat. No.5,112,678 to Gay et al (referred to herein as the '678 patent). Therelatively fire-resistant web of the '678 patent has also served well asan underlayment in a U.L. Incorporated fire-resistant rated roofingsystem over wooden decks, etc. For many years this material has servedthe building construction industry, e.g., as the facer for the laminatedfoam board product taught in U.S. Pat. No. 5,001,005. The foam board ofU.S. Pat. No. 5,001,005 remains an important and integral part of bothroofing and side-wall insulation.

FIG. 1 shows a prior art coating method suitable for applying coatingssuch as those of U.S. Pat. No. 5,112,678. A raw glass mat 10 (e.g., the“substrate”) enters a coating station at a level lower than a top of anapplicator roll 12. The direction of travel of the glass mat 10 isparallel to a “machine direction” (M.D.) of a facer produced by themachine, while a dimension perpendicular to the machine direction andperpendicular to the plane of FIG. 1 is understood to be parallel to a“cross machine direction” (C.M.D.) of a resultant facer similarlyoriented. The applicator roll is driven to rotate about its axis (eitherclockwise or counterclockwise, as depicted by arrow 13). A coating pan14 is filled with a coating mix 16 up to a level that is sufficient forthe applicator roll 12 to pull an adequate amount of coating to the topof the applicator roll 12. The speed of rotation of applicator roll 12is used to get adequate amounts of coating mix 16 up into the glass mat10 as the glass mat 10 is conveyed. In its path of conveyance, the glassmat 10 extends around applicator roll 12 in a wrap-arc 18. A scraperblade 20 is placed so that the excess coating scraped off returns intothe coating pan 14. After the excess is scraped off, the coated matproceeds into a dryer section (not shown) where the coated glass matfacer 22 is dried and wrapped into rolls.

The prior art process of FIG. 1 is characterized by a wrap arc 18 at theapplicator roll 12 and a wrap angle 28 at the scraper blade 20.Conventionally, the wrap arc 18 on the applicator roll 12 is less than30 degrees, and typically less than 20 degrees. The wrap angle 28 aroundthe scraper bar 20 is conventionally slightly less than 180-degrees;e.g., 175-degrees.

In the construction industry, building materials are often analyzed todetermine their performance vulnerabilities or weak points. Avulnerability for a laminated board made with a coated glass mat facercan be the structural integrity of the glass mat which comprises thefacer. In other words, how well the glass mat of the facer holdstogether under stress, e.g., the cohesive strength (or lack of strength)of the glass mat, is an important indicia of material quality.Experience has generally shown that the cohesive strength of any glassmat is typically too low to resist the pulling-away force of high windshear vacuums, whether the glass mat be incorporated either in a stuccowall or under a fully adhered single-ply membrane roofing system.

One factor influencing structural integrity of a building material whichincorporates a coated glass mat is the degree to which glass fiberscomprising the mat are uncovered. Uncovered glass fibers are exposed andthus more subject to deleterious forces.

The complications of using coated glass mats as ingredients in buildingmaterials such as a board are compounded when the glass mats interfacewith certain other materials which comprise the board core. One exampleof such a complicating material is Gypsum. Most gypsum boardapplications are more difficult, and much stronger coated glass mats arerequired. While the problems presented by gypsum could perhaps be solvedby using heavier raw glass mat substrates, such an option is quiteexpensive. A challenge, therefore, is strengthening the coated glass mat(e.g., strengthening the facer) without substantially increasing costs.

The history of gypsum board development has passed many milestones, manyof these milestones being related to the surfaces, or facers, coveringthe broad surface of a gypsum board. In almost all cases, the subject offacer stability was an issue. Also the facers have had to resistweathering as well as retaining constant dimensions. Mildew and moldhave been a problem with the original multi-ply paper facers used ongypsum board. Unfortunately, the paper facers also might not allow watervapor to escape. Yet the escape of water vapor is essential in curingthe gypsum. While these paper facers have been modified with chemicalsto improve their properties, most of the gypsum board progress andsuccess has come by changing from paper facers to fiberglass mat facers.

The entire scope of manufacturing different facer materials for buildingproducts is extensive, encompassing both fields of gypsum boardfiberglass facers and thermosetting polyiso foam insulation boardfacers. In recent years, many facer-related methods and products thereofhave been taught in United States patents such as the following (all ofwhich are incorporated herein in their entirety by reference):

3,284,980 3,993,822 4,504,533 4,637,951 4,647,496 4,784,897 4,810,5694,879,173 5,112,678 5,148,645 5,171,366 5,220,762 5,319,900 5,342,5665,342,680 5,371,989 5,395,685 5,397,631 5,401,588 5,552,187 5,601,8885,644,880 5,665,442 5,718,785 5,791,109 5,945,182 5,945,208 5,965,2576,001,496 6,146,705 6,299,970

As alluded to above, some coated glass mat prior art facer products areineffective or unusable as a facer for a gypsum board. For example thecoated glass mat of U.S. Pat. No. 5,965,257 shows signs of dissolvingwhen subjected to a stream of running water, and has low tensile testnumbers (e.g., when compared to the mat made from the '678 patent).

A gypsum board used in construction is much heavier than a low density,lightweight insulation foam board. The gypsum board must have enoughstructural strength to avoid breaking while being handled duringinstallation. The facers of gypsum board provide most of the structuralstrength needed. The prior art multi-ply paper-board facers possessample tensile strength for use as facers. However, the ordinary priorart coated glass mat facers do not have adequate tensile strength. Inaddition to lacking tensile strength, ordinary coated glass mat facerscan face difficulty in becoming adequately bonded to the gypsum slurry.

Thus, as indicated above, conventionally a laminated board has a corewhich is sandwiched between two facers, the facers each comprising acoating material on a glass mat. It is the interface between the coreand the glass mat where failure can occur under conditions of highstress in the “pull-apart” direction. As previously mentioned, thefailure occurs because some fibers are left uncovered and the bondingstrength of the so-called “binder” material between individual glassfibers is not strong enough to prevent failure. Just after a non-wovenglass mat is formed on a drainage wire, a complex binder chemical isadded, but this is barely strong enough to hold individual fiberstogether.

U.S. Pat. No. 4,647,496, U.S. Pat. No. 4,810,569, U.S. Pat. No.5,371,989, U.S. Pat. No. 5,644,880, and U.S. Pat. No. 6,001,496, showhow a glass mat can be partially imbedded in gypsum board but leaveloose glass fibers on the surface.

In a gypsum board process which utilizes a coated glass mat in a facer,a fine balance must be achieved. If the coated glass mat facer has toomuch glass mat exposed such that the gypsum cannot cover it essentiallyentirely, the resultant board is unacceptable. On the other hand, if notenough glass fibers (which serve to anchor the gypsum) are left exposed,the resultant board is not acceptable. In both cases, the finished boardcan fail a flexural stress test, or worse, break at the job-site. Thus acoated glass mat facer must have both adequate tensile strength plus theability to become tightly bonded and intermeshed with gypsum slurrybefore it hardens. Since prior art facers did not suffice, there remainsa need for an unique coated glass facer to use in creating a gypsumboard having a mold resistant, weather-proof surface, and strongflexural test results.

What is needed, therefore, and an object of the present invention, is acoated is glass mat which has enhanced tensile strength, as well asmethods for fabricating such mat.

BRIEF SUMMARY

A coated glass mat comprises a glass mat substrate having non-wovenglass fibers and a coating. The coating essentially uniformly penetratesthe glass mat substrate to a desired fractional thickness of the coatedglass mat. The coating imparts a tensile strength to the coated glassmat which on average is at least 1.33 times greater than the tensilestrength of the glass mat substrate without the coating. On average, theweight of the coated glass mat per unit area is no more than about sixtimes the weight of the glass mat substrate prior to coating.

In example embodiments, penetration of the coating into the glass matsubstrate preferably extends to a depth of from twenty five percent ofthe thickness of the coated glass mat to seventy five percent of thethickness of the coated glass mat. Moreover, a non-coated thickness ofthe coated glass mat is sufficiently thick for bonding purposes with,e.g., a gypsum slurry or other core materials such as thermoplastic orthermosetting plastics.

The coating comprises a coating blend which provides the coated glassmat with a porosity sufficient to allow water vapor to escape from agypsum slurry when heated. Preferably, such porosity is in a range fromabout 1.3 Cubic Feet per Minute (CFM) (all CFM data given are also “persquare foot per”) to about 5.0 CFM. The coating is preferably a coatingblend comprised of water, latex binder, inorganic pigment, and inorganicbinder.

The raw glass mat substrate has a weight which is between about twelve(12) pounds per thousand square feet and about fifty (50) pounds perthousand square feet. In one example, the glass mat substrate beforecoating weighs about fourteen and a half (14.5) pounds per thousandsquare feet. After coating the coated glass mat has a tensile strengthwhich on average is greater than one hundred twenty pounds perthree-inch width. In another example, the glass mat substrate beforecoating weighs about twenty-six and a half (26.5) pounds per thousandsquare feet. After coating the coated glass mat has a tensile strengthwhich on average is greater than two hundred twenty pounds perthree-inch width.

New coating methods which yield the coated glass mat expose a sufficientamount of coating to the glass mat to provide a uniform depthpenetration and thereby achieve the increased tensile strength. Themethod facilitates a high degree of coating depth penetration (e.g., upto 75%) and yet no significant change in coating percentage compositionby weight per square unit area. Because of the new coating techniques,the prior art glass mat substrate has a disproportionate increase intensile strength relative to the increase in final product weight. Thecoated glass mat webs are much stronger and more weatherproof than priorart similar webs.

One of the new coating techniques involves increasing a wrap angle ofthe glass mat substrate around an applicator roll thereby increasingexposure of the coating to the glass mat substrate. Other techniquesalso provide a substantial increase in tensile strength.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of apparatus utilized in prior art coatingprocess for a glass mat.

FIG. 2 is a schematic view of apparatus utilized in a coating processwhich achieves improved coating exposure and uniform penetration.

FIG. 3A is a schematic cross-sectional view of a section of a side viewof a coated glass mat fabricated in accordance with Example 1.

FIG. 3B is a photomicrograph of a coated glass mat fabricated accordingto Example 1.

FIG. 4A is a schematic cross-sectional view of a section of a side viewof a coated glass mat fabricated in accordance with Example 4.

FIG. 4B is a photomicrograph of a coated glass mat fabricated accordingto Example 4.

FIG. 5A is a schematic cross-sectional view of a section of a side viewof a coated glass mat fabricated in accordance with Example 5.

FIG. 5B is a photomicrograph of a coated glass mat fabricated accordingto Example 5.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particularcompositions, techniques, etc. in order to provide a thoroughunderstanding. However, it will be apparent to those skilled in the artthat the present invention may be practiced in other embodiments thatdepart from these specific details. In other instances, detaileddescriptions of well known substances and methods are omitted so as notto obscure the description of the present invention with unnecessarydetail. It will be further understood that in the ensuing descriptionand claims that the terms “web” and “mat” are employed interchangeably,and in the sense that the mats and webs can be used as “facers”, allthree terms may be utilized interchangeably.

A coated glass mat suitable for use, e.g., as a facer in a gypsum boardis formed by a process which uses a substantially porous, predominatelyglass mat substrate. The glass mat substrate comprises non-woven glassfibers. The coating of the coated glass mat advantageously penetratesdeeply into the thickness of the mat, e.g., from approximately 25% up to75% of the mat thickness, thereby affording higher tensile strengths. Towhatever depth in this range (25% up to 75% of the mat thickness) thecoating extends, it does so essentially uniformly. The uniformly deeppenetration is achieved by one or more new coating techniques whichfacilitate increased exposure of coating mixture to a glass matsubstrate, thereby achieving more uniform coating penetration. Yetcompared to prior art mats the coated glass mat has about the samecoating percentage composition by weight per square unit area. Theuncoated thickness (e.g., approximately 25% up to 75% of the thickness)of the glass mat is sufficiently thick for bonding purposes with, e.g.,a gypsum slurry or other core materials such as thermoplastic orthermosetting plastics. The raw, uncoated glass mat substrate has aweight which is between about twelve (12) pounds per thousand squarefeet and about fifty (50) pounds per thousand square feet. An examplecoating batch for use in forming the coated glass mat is provided inExample 1.

The porosity of the coated glass mat is sufficiently low that it is notpenetrable by gypsum slurry, yet porous enough to allow water vapor toescape from the gypsum slurry when heated, and porous enough to allowthermoplastic or thermosetting plastics, or gypsum slurry, to completelycover essentially all exposed, individual glass fibers. Preferably theporosity of the coated glass mat is in a range of from about 1.3 CFM(cubic feet per minute per square foot) to about 5.0 CFM.

The improved coating techniques thus facilitate increased exposure ofthe coating mixture to a glass mat substrate, and thereby a uniformlydeeper penetration of the coating into the interior spaces of the glassmat. The penetration is to a depth of at least 25%, but preferably lessthan about 75%, of the thickness of the mat, i.e., not so far that itpenetrates entirely. Such increased exposure and uniformly deeppenetration is accomplished by various techniques including but notlimited to those hereinafter specifically described.

Mechanical techniques for achieving the increased exposure and uniformcoating penetration depth in the glass mat include the following asexamples: (1) selecting a proper wrap angle for the scraper blade (indegrees of angle); and, (2) selecting a proper wrap arc on theapplicator roll (in degrees). One, or the other, or both, may beemployed, but it must be noted that the wrap angle at the scraper bladeis dependent upon the degree of wrap-arc at the applicator roll, andvice versa. An example mode of the wrap selection technique is describedbelow with reference to FIG. 2.

FIG. 2 shows basic apparatus utilized in an example mode of the improvedcoating process which achieves the desired increased exposure of thecoating mixture to the glass mat substrate. Structural elements of theFIG. 2 apparatus which correspond to elements of the FIG. 1 apparatushave same least two significant digit reference numbers.

In contrast to the prior art process of FIG. 1, the process implementedby the FIG. 2 apparatus utilizes a higher degree of wrap-arc 118 aroundthe applicator roll 112 and a smaller (less than 180-degrees) wrap angle128 around scraper blade 120. This tighter wrapping method provides anincreased exposure of coating mixture 116 to the glass mat substrate110, and thereby a higher degree of uniform coating penetration into theglass mat. The degree of penetration is between approximately 25% up to75% of the thickness into the glass mat substrate. In this coatingmethod, the wrap-arc 118 is much larger (above about 20-degrees) thanwrap-arc 18 of FIG. 1. Specifically, wrap-arc 118 is in a range fromabout 20 degrees to 80 degrees depending upon other operationalparameters (such as, for example, speed of applicator roll 112).Likewise, wrap angle 128 of the new method is noticeably sharper thanwrap angle 28 of the prior art (about 170 degrees).

It should be understood that it is the degree of exposure of the coatingmaterial 116 to the glass mat substrate 110 that is increased by the newprocessing techniques and which results in the more uniform penetrationof the coating into the glass mat substrate. The degree of exposure oravailability of the coating 116 is a different phenomena than the actualamount of acquisition by glass mat substrate 110 of the coating mixture.Indeed, using the new exposure enhancing technique, no more coating isactually applied for penetration into the glass mat substrate. Rather,there is more opportunity for uniform acquisition of the coating 116 bythe glass mat substrate 110.

The coating industry has used the “1-Roll Kiss Coater” for many years. Akiss-roll applicator is normally followed by a grooved rod, but glassmat will destroy such a rod in a matter of minutes. However, amodification to the trailing blade method does work when, if an excessamount of relatively low viscosity coating mix 116 is applied to thebottom surface of the glass mat 110, the excess is scraped off withblade 120. It is believed that the combination of a kiss-roll followedby a monolithic scraper blade is a new and unique combination.

Although FIG. 2 and other drawings are not necessarily to scale, therelative dimensions have been depicted to show actual spatialrelationships. They only approximately represent the path of a raw glassmat substrate as it passes through a coating station. The approximatewrap angles 118 over applicator roll 112 and 128 over the scraper blade120 are shown to represent a definite deviation from zero wraps.

In lieu or in addition to the proper setting of wrap arc 118 and wrapangle 128, there are at least eight (8) other techniques that can beutilized to increase the degree of exposure of the coating 116 to theglass mat substrate 110. These techniques are: (1) adjusting the speedof the coating line; (2) adjusting the viscosity of the coating mix; (3)adjusting the direction of the applicator roll rotation; (4) selecting aproper diameter of the coating applicator roll; (5) adjusting the speedof the applicator roll rotation; (6) selecting a proper surface materialof the applicator roll; (7) controlling the thickness of the glass matweb; and (8) controlling the porosity, in cubic feet of air per minuteper square foot, of the glass mat web.

It was mentioned previously that the wrap-arc 118 is in a range of fromabout 20 degrees to 80 degrees. In one example, the wrap-arc 118 extendsabout 80 degrees and the applicator roll is rotated at a nominal angularvelocity which is just slightly faster than the linear velocity of theglass mass substrate. Yet in another example, the wrap-arc 118 extends alesser amount (e.g. 40 degrees), but the applicator roll is driven at anincreased angular velocity which affords essentially the same exposureas the first example. Thus, the new techniques can be combined in orderto achieve the desired exposure of the coating 116 to the glass matsubstrate 110, thereby enhancing uniform coating penetration. Theuniform coating penetration facilitates the improved tensile strength ofthe coated glass mat, e.g., a tensile strength in the machine directionwhich is at least 1.33 times greater than that of the glass matsubstrate prior to coating.

Thus it will be understood that various mechanical ones of thetechniques aforementioned can be employed to increase exposure of thecoating 116 to the substrate 110 in a comparable manner. Usage of thesetechniques presumes, however, that the viscosity of the coating 116 isin a suitable range, and has sufficient solids content. That is, thecoating 116 must be sufficiently viscous that it does not fly off themat during the travel between applicator roll 112 and blade 120, and yetnot so viscous that it cannot be picked up by applicator roll 112.

In a preferred mode, an electric motor driven, chrome plated applicatorroll 112 is used. However, it is possible to use rubber or plasticcoated rolls, or stainless steel rolls. The applicator roll 112 ispowered to rotate in same direction as the web, and rotated slightlyfaster than the web. The scraper blade 120 can be made of either carbonsteel, or hardened steel, or spring steel, or tungsten-carbide steel, orfrom various grades of ceramics. The wrap angle 128 on the blade 120 isfrom about 170-degrees to about 175-degrees, and the wrap arc 118 on theroll 112 is about 20-degrees to about 80-degrees, depending on othervariables.

The prior art coating mixes can be utilized with the uniformly deeperpenetration processing techniques herein described. For example, in onemode, filler materials containing some naturally occurring inorganicbinder are deliberately chosen. These fillers with naturally occurringbinders must be of a suitable mesh size. The minimum allowable qualityis where at least 85% by weight of the filler passes a 200-mesh screen(Grade 85/200). Examples of such fillers having the naturally occurringbinder are, but are not limited to: limestone containing quicklime(CaO), clay containing calcium silicate, sand containing calciumsilicate, aluminum trihydrate containing aluminum oxide, and magnesiumoxide containing either the sulfate or chloride of magnesium, or both.The filler, gypsum, can be both a mineral pigment (as gypsum dihydrate)and a binder (as gypsum hemi-hydrate), but gypsum is slightly soluble inwater, and the solid form is crystalline making it a brittle and weakbinder.

Various examples are now described for contrasting coated glassfabricated with prior art coating processes (see Example 1 and Example2) with coated glass mats which utilize the increased exposuretechniques herein described.

Example 1 Prior Art

For Example 1, a batch of coating mixture is made by adding 3,200 poundsof water to a mixing tank having a low speed mixer. This is followed by80 pounds of a sodium salt of poly-naphthylmethanesulfonate dispersingagent, such as Galoryl® DT 400 N. Then is added 950 wet pounds (498.8dry pounds) of a carboxylated SBR latex, such as Styrofan® ND5406,followed by 11,000 pounds of 85/200 (85% passes a 200-mesh screen)limestone that contains about 70 pounds of calcined lime (CaO). Thisproduces a 15,230-pound batch of coating mixture having about 75.7%solids and with a viscosity of about 300 centipoise (cps) at 25° C. Thequicklime (CaO) content is about 0.6% by weight on the total dry-weightbasis. The latex solids comprise about 4.3% on the dry weight basis.

The coating mixture of Example 1, produced in accordance with U.S. Pat.No. 5,112,678, was (for Example 1) applied using the prior art processof FIG. 1 to a non-woven glass mat Dura-Glass® 7503 made by JohnsManville. The glass mat weight averaged about 13.9-lbs/MSF (thousandsquare feet), and had a thickness average of about 0.023-inches. Thefinal coated product weight averaged about 84.8-lbs/MSF, indicating thatthe coating solids added 70.9-lbs/MSF.

FIG. 3A depicts a section of a side view of a coated glass mat 40(3)made fabricated in accordance with Example 1. The coated glass mat ofFIG. 3A is made from the 14.5-lbs/MSF raw glass mat substrate(Dura-Glass® 7503), with a final coated product weight averaging about85.0-lbs/MSF (indicating that the coating solids added 70.5-lbs/MSF).For the coated glass mat of FIG. 3A, the thickness dimension(represented by reference numeral 42(3)) is about 0.026-inches. Themeasured thickness of the coating penetration is depicted by arrow44(3), while the thickness of the portion remaining uncoated is labeledby arrow 46(3).

By the use of common laboratory microscope, it was discovered that ofthe total finished mat thickness of FIG. 3A, the coating materialpenetrates from about 10% up to about 25%. Said another way, the ratioof coating penetration thickness 44(3) to non-coated thickness 46(3) isabout 25 to 75. The portion having the uncoated glass fibers is employedin holding the core material (e.g., polyiso foam), making a reasonablystrong laminated panel as taught by U.S. Pat. No. 5,001,005. Aphotomicrograph of a coated glass mat according to Example 1 is shown inFIG. 3B.

Table 1 shows thirty (30) samples of tensile test data generated for thecoating and prior art processing techniques of Example 1, as well asaverage tensile test data, a standard deviation, and a range. For eachsample, tensile test data for the resultant coated glass mat is suppliedin column 1 with respect to the machine direction (M.D.), and in column2 with respect to the cross-machine direction (C.M.D.) dimension of theglass mat. All tensile strength values provided herein (including thoselisted in Table 1 and other tables) are in units of pounds per threeinch wide strip of coated glass mat.

Prior to coating, the glass mat substrate of Example 1 had an averagenominal tensile strength in the machine direction of 90 pounds per threeinch width and an average tensile strength in the cross machinedirection of 60 pounds per three inch width. From Table 1 it can be seenthat the coating imparts a tensile strength to the coated glass matwhich, on average, is less than 1.10 times greater in the machinedirection than the tensile strength of the glass mat substrate in themachine direction prior to coating.

TABLE 1 Example 1 Example 1 Sample # M.D. C.M.D.  1 116 97  2 118 99  388 74  4 87 68  5 89 61  6 86 72  7 96 88  8 87 80  9 112 88 10 118 9111 95 71 12 99 82 13 97 78 14 87 68 15 90 75 16 84 64 17 96 72 18 76 6619 88 66 20 86 77 21 95 80 22 90 76 23 116 99 24 100 98 25 102 82 26 11478 27 116 99 28 114 98 29 112 98 30 110 94 Average 98.8 81.3 Std. Dev.12.6 12.2 Range 42.0 38.0

Example 2 Prior Art

As Example 2, a coated glass mat facer fabricated by Elk Corporation inaccordance with the prior art process of U.S. Pat. No. 5,965,257 andknown as “ISO FACER 1” was evaluated. The coated glass mat facer ofExample 2 weighed about 99-lbs/MSF, and measured (with a caliper) athickness of about 0.034-inches. Thirty samples of tensile test data forthe mat of Example 2 are shown in Table 2, the first column of Table 2showing tensile test data with respect to the machine direction (M.D.)and the second column showing tensile test data with respect to thecross-machine direction (C.M.D.).

Comparison of the tensile strengths for Example 1 and Example 2 as setforth in Table 1 and Table 2, respectively, show that even with morethickness and higher weight, the product of Example 2 is considerablyweaker than the product made as Example 1. Yet both Example 1 andExample 2 pale in contrast to the substantially higher tensile strengthsachieved by the remaining Examples, the higher tensile strength beingadvantageously achieved without increases in weight or thickness.

TABLE 2 Example 2 Example 2 Sample # M.D. C.M.D.  1 89 54  2 93 70  3 8363  4 88 58  5 83 59  6 92 62  7 87 55  8 77 65  9 106 70 10 98 62 11 7859 12 69 55 13 75 58 14 79 60 15 107 82 16 100 78 17 73 51 18 72 54 1974 62 20 71 68 21 61 47 22 68 54 23 72 56 24 68 38 25 69 57 26 89 75 2774 40 28 91 79 29 72 40 30 79 46 Average 81.2 59.2 Std. Dev. 11.9 11.2Range 46.0 44.0

Concerning the data of Table 1 and Table 2, the sample size tested was3-inches wide by 10-inches long, with 1-inch at each end inside thejaws, and the tensile test jaws were pulled at the speed of 1-inch perminute. Those familiar with test results of uncoated glass mat will notethat the Standard Deviation is very similar to the tensile test Sigma ofplain glass mat. In other words, the wide range of test scores fortensile testing are built into the glass mat as produced, and coatingthe mat has no effect on that wide range other than raise the individualnumbers.

Example 3

Example 3 utilized the same coating batch mixture as Example 1. Thecoating of Example 3 was applied to a glass mat using the process ofFIG. 2. The glass mat weighed 14.5-pounds per MSF (thousand squarefeet).

Table 3 shows samples of tensile strength data for Example 3. As withthe Table 4 mats discussed subsequently, for the Table 3 mats the samplesize tested was 3-inches wide by 10-inches long, with 1-inch at each endinside the jaws, and the tensile test jaws were pulled at the speed of1-inch per minute. The coated glass mats of Example 3 had an averagethickness of 0.026-inches and weighed an average of 85-lbs per1,000-square feet (MSF). Of that finished weight, about 70.5-lbs/MSF wascoating and 14.5-lbs/MSF was glass mat.

TABLE 3 Sample # Machine Direction Cross Mach. Dir. 1 101.6-lbs/3-inch114.1-lbs/3-inch 2 113.5-lbs/3-inch 111.8-lbs/3-inch 3 140.2-lbs/3-inch113.1-lbs/3-inch 4 116.9-lbs/3-inch 102.9-lbs/3-inch 5 120.5-lbs/3-inch 95.5-lbs/3-inch 6 110.9-lbs/3-inch 119.7-lbs/3-inch 7 111.5-lbs/3-inch108.0-lbs/3-inch 8 129.3-lbs/3-inch 126.7-lbs/3-inch 9 159.8-lbs/3-inch108.0-lbs/3-inch 10  141.8-lbs/3-inch 127.9-lbs/3-inch 11 135.5-lbs/3-inch 140.8-lbs/3-inch 12  130.5-lbs/3-inch 144.0-lbs/3-inch13   83.5-lbs/3-inch  96.0-lbs/3-inch 14  113.8-lbs/3-inch106.0-lbs/3-inch 15  112.5-lbs/3-inch 114.9-lbs/3-inch 16 134.5-lbs/3-inch 105.8-lbs/3-inch 17  126.8-lbs/3-inch  84.6-lbs/3-inch18  141.7-lbs/3-inch 123.3-lbs/3-inch Average 123.6-lbs/3-inch113.5-lbs/3-inch Std. Dev. 17.8 15.3

Prior to coating, the glass mat substrate of Example 3 had an averagenominal tensile strength in the machine direction of 90 pounds per threeinch width and an average tensile strength in the cross machinedirection of 60 pounds per three inch width. From Table 3 it can be seenthat the coating imparts a tensile strength to the coated glass matwhich, on average, is at least 1.33 times greater in the machinedirection than the tensile strength of the glass mat substrate in themachine direction prior to coating. In particular, for Example 3 thecoating imparts a tensile strength to the coated glass mat which is, onaverage, 1.37 times greater than the tensile strength of the glass matsubstrate prior to coating. When the term “tensile strength” is utilizedherein without reference to direction, it is understood to refer totensile strength in a machine direction.

The constituency of the coating and degree of application of the coatingfor Example 3 is such that, on average, the weight of the coated glassmat per unit area after coating is no more than six times the weight ofthe glass mat substrate before coating. That is, the coating weight isless than five (5) times the weight of the glass mat substrate (prior tocoating). The average porosity for the coated glass mat of Example 3 isbetween 3.8 CFM and 3.9 CFM.

Example 4

The coating batch for Example 4 was the same as for Example 1, but wasapplied using the process of FIG. 2 to a glass mat (Dura-Glass 7503)sold as weighing 14.5-pounds per MSF (thousand square feet), butactually weighing 14.9-pounds per MSF. The coated glass mat weighed89.1-pounds per MSF on average. As with the Example 1 mats, the Example4 mat sample size tested was 3-inches wide by 10-inches long, with1-inch at each end inside the jaws, and the tensile test jaws werepulled at the speed of 1-inch per minute. Approximately the same coatingweight was applied (an average of 74.2-pounds/MSF), but the improvedprocessing techniques made the coating penetrate more uniformly andfurther into the glass mat substrate. In doing this, the approximatesame coating weight created a final product with substantially highertensile strength, as indicated by Table 4.

TABLE 4 Example 4 Tensile Data Sample # M.D. C.M.D.  1 122 110  2 114108  3 141 113  4 117 103  5 121 96  6 123 120  7 112 108  8 129 125  9150 108 10 141 127 11 135 120 12 130 138 13 130 121 14 134 101 15 128114 16 134 105 17 126 97 18 141 98 19 121 100 20 143 128 21 140 98 22110 98 23 121 109 24 146 105 25 148 110 26 138 106 27 135 97 28 141 10429 138 102 30 143 104 Average 131.7 109.1 Std. Dev. 11.1 10.8 Range 40.042.0

FIG. 4A depicts a cross section of a coated glass mat 40(4) fabricatedin accordance with Example 4. The thickness dimension (represented byreference numeral 42(4)) of coated glass mat 40(4) is about0.026-inches. The measured thickness of the coating penetration isdepicted by arrow 44(4), while the thickness of the portion remaininguncoated is labeled by arrow 46(4). By the use of a common laboratorymicroscope, it was discovered that of the total finished mat 40(4)thickness (0.026 inches), the coating material penetrates about 70%(seventy percent), or about 0.014-inches. Said another way, the ratio of44(4) to 46(4) is about 70-to-30. The portion of uncoated glass fibersthat successfully hold gypsum slurry and other core materials such asthermoplastic and thermosetting plastics. FIG. 4B is a photomicrographof a coated glass mat fabricated according to Example 4.

Prior to coating, the glass mat substrate of Example 4 had an averagenominal tensile strength in the machine direction of 90 pounds per threeinch width and an average tensile strength in the cross machinedirection of 60 pounds per three inch width. From Table 4 it can be seenthat the coating imparts a tensile strength to the coated glass matwhich, on average, is at least 1.33 times greater in the machinedirection than the tensile strength of the glass mat substrate in themachine direction prior to coating. In particular, for Example 4 thecoating imparts a tensile strength to the coated glass mat which is, onaverage, 1.46 times greater than the tensile strength of the glass matsubstrate prior to coating.

The constituency of the coating and degree of application of the coatingfor Example 4 is such that, on average, the weight of the coated glassmat per unit area after coating is no more than about six times theweight of the glass mat substrate before coating. That is, the coatingweight is less than five (5) times the weight of the glass mat substrate(prior to coating). The average porosity for the coated glass mat ofExample 4 is between 1.5 CFM and 1.6 CFM.

The tensile strengths of the glass mat facers of Example 4 which havethe deeper coating penetration are 62.2% better in the machine direction(M.D.), and 84.3% better in the cross machine direction (C.M.D.) thanthe glass mat facers of Example 2; and, 33.3% better in the machinedirection (M.D.), and 34.2% better in the cross machine direction(C.M.D.) than the glass mat facers of Example 1.

Example 5

The coating batch for Example 5, like that of Example 4, was the same asfor Example 1, but was applied using the process of FIG. 2 to a glassmat (Dura-Glass 7503) weighing 26.5-pounds per MSF (thousand squarefeet). The Example 5 mat sample size tested was 3-inches wide by10-inches long, with 1-inch at each end inside the jaws, and the tensiletest jaws were pulled at the speed of 1-inch per minute. The tensilestrength for the mats of Example 5 are shown in Table 5.

FIG. 5A is a side cross-sectional view of a coated glass mat 40(5)fabricated in accordance with Example 5. Example 5 utilized a heavierand stronger glass mat substrate weighing 26.5-pounds per MSF (thousandsquare feet). In FIG. 5A, the total thickness dimension depicted byarrow 42(5) is about 0.036-inches thick. In the Example 5 coated mat40(5), the coating permeates into the glass mat to a depth depicted byarrow 44(5), leaving an uncoated portion of thickness indicated by arrow46(5). The thickness (depicted by arrow 42(5)) of the total finishedcoated mat 40(5) is on the order of 0.036-inches. Microscopic analysisshows that the coating material penetrates to about 75% (seventy-fivepercent), or 0.027-inches. Thus the ratio of coated thickness touncoated thickness is about 75-to-25. Although the coated mat 40 ofExample 5 comprises a lower total weight of coating, the coatingpenetrates to a greater thickness, thereby covering more glass fibers.Therefore, the coating is less dense. FIG. 5B is a photomicrograph of acoated glass mat fabricated according to Example 5.

The weight of this finished product of Example 5 was 87.5-lbs/MSF,surprisingly only 3.2% heavier than the prior art coated mat using14.5-lbs/MSF glass mat substrate. The Example 5/Table 5 coated glass matis comprised of 26.5-lbs/MSF of uncoated glass mat (substrate) plus only61.0-lbs/MSF coating. The amount of the coating added was lower than forthe coated mats of Table 1 and Table 2 (e.g., the coated mats which usedthe 14.5-lbs/MSF mat) The lighter mat consistently picked up over70.0-bls/MSF, whereas the 26.5-lbs/MSF mat picked up only 61.0-lbs/MSF.

TABLE 5 Sample # Machine Direction Cross Mach. Dir. 1 226.8-lbs/3-inch214.0-lbs/3-inch 2 227.5-lbs/3-inch 184.4-lbs/3-inch 3 274.8-lbs/3-inch167.5-lbs/3-inch 4 229.1-lbs/3-inch 168.4-lbs/3-inch 5 305.1-lbs/3-inch176.1-lbs/3-inch 6 275.0-lbs/3-inch 174.2-lbs/3-inch 7 312.5-lbs/3-inch176.1-lbs/3-inch 8 261.5-lbs/3-inch 267.5-lbs/3-inch 9 294.8-lbs/3-inch256.5-lbs/3-inch 10  299.6-lbs/3-inch 210.9-lbs/3-inch Average270.7-lbs/3-inch 199.6-lbs/3-inch Std. Dev. 33.3 36.8

Prior to coating, the glass mat substrate of Example 5 had an averagenominal tensile strength in the machine direction of 90 pounds per threeinch width and an average tensile strength in the cross machinedirection of 80 pounds per three inch width. From Table 5 it can be seenthat the coating imparts a tensile strength to the coated glass matwhich, on average, is at least 1.33 times greater in the machinedirection than the tensile strength of the glass mat substrate in themachine direction prior to coating. In particular, for Example 5 thecoating imparts a tensile strength to the coated glass mat which is, onaverage, 3.00 times greater than the tensile strength of the glass matsubstrate prior to coating.

The constituency of the coating and degree of application of the coatingfor Example 5 is such that, on average, the weight of the coated glassmat per unit area after coating is no more than six times the weight ofthe glass mat substrate before coating. In particular, for Example 5 theweight of the coated glass mat per unit area after coating is only about3.3 times the weight of the glass mat substrate before coating. That is,the coating weight is less than five (5) times the weight of the glassmat substrate (prior to coating).

So with a very small increase in total product weight (3.2% increase),the tensile strength in the machine direction was improved 274%(270.7/98.8×100), and in the cross-machine direction by 246%(199.6/81.3×100). This average increase of about 260% in overall tensilewas better than expected.

The weights of the particular glass mat substrates described inconjunction with the tensile strength enhancement examples hereof arejust examples. It should be understood that any glass mat weighing morethan 12.0-pounds per MSF, but preferably between 14.0-pounds per MSF and30.0-pounds per MSF, may be used with the new techniques hereindisclosed. Inappropriate (e.g., lighter weight) glass mats do notachieve the unusually high tensile strengths that are obtained by addingless coating to heavier glass mats. Appropriate weight glass mats areobtained from Saint-Gobain Vetrotex America, Inc. and Johns Manville.

In view of the fact that the coated glass mats described herein havemore uniform penetration of coating into the glass mat, the coatingbinds far more glass fibers together than the coating of the prior artcoated glass mat. The latex binder of the coating is apparently betterutilized, thus providing much higher tensile strengths. Moreimportantly, the coating binder spreads out more uniformly to fill moreglass fiber interstices, thereby enhancing the strength.

The coated glass mat is advantageously employed in a laminate product.By eliminating uncovered glass fibers in a laminate product, essentiallyall of the coating meets up against the core (e.g., Gypsum or polyisofoam insulation sandwiched between the two coated glass mat facers).With essentially all of the glass fibers having a contiguous covering ofeither coating or core material, the cohesive strength of ordinary glassmats becomes a mute point. The bonding strength between core materialand the coating is known to be good. The increased exposure of coatingmix to the glass mat substrates thus affords sufficient volume ofnon-coated glass fibers to form an excellent bond with the gypsumslurry. The substantial improvement in coated glass mat tensile strengthplus the excellent bond to the cured gypsum board creates a highflexural test result, well above the minimum requirement of the gypsumboard product. The greater thickness of uncoated glass mat proved to bedetrimental in attempts to impregnate the additional thickness withpolyiso foam, for example.

The heavier weight glass mat was expected to pick up correspondinglymore coating weight. Manufacturing engineers had anticipated a need torun the coaters substantially slower. However, the heavier glass matpicked up a lower mass of coating instead of a higher mass. It wasdiscovered that while the coater did need to run slower to accomplishcomplete dryness, the speed reduction was not the magnitude expected.

Another benefit discovered when utilizing the lower density (lesscoating mass covering more glass mat volume) coating was that when usedas a facer for gypsum its porosity was perfect. This means it was denseenough to prevent gypsum slurry from penetrating, yet not too dense tocauses the facer to blow off from escaping steam.

The enhanced tensile strength coated glass mat advantageously has theability to intertwine with a gypsum slurry and to combine to produce ahigh flexural strength in a three-dimensional board, made of gypsum orother core materials such as thermoplastic or thermosetting plastics.The coated glass mat or web also has good weather-proof characteristics,while at the same time having excellent mold-growth resistance.

The enhanced tensile strength coated glass mat has enough porosity toallow the gypsum to “breathe-out” water vapor while still processing yetnot allow gypsum slurry to leak through into the processing machinery.

Thus, an improvement that was anticipated to be much more costly andgenerally onerous to manufacture turned out to be only slightly morecostly and no more difficult to produce.

Further, the enhanced tensile strength coated glass mat has enoughfibers available to bond well with the cured gypsum, without leaving toomuch glass fiber thickness such that the wet gypsum slurry does notpenetrate enough to cover all the loose fibers.

While providing the above mentioned desirable properties, the coatedglass mat/facer remains a low-cost product due, e.g., to its usingeconomy grade limestone in rich abundance and very little of thehigh-cost polymer latexes.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A coated glass mat comprising: a glass mat substrate having non-wovenglass fibers; and a coating comprising latex binder and inorganicpigment, said coating being present in an amount of about 61 lbs/MSF toabout 75 lbs/MSF and being only partially permeated into said substratewhile also imparting a tensile strength to the coated glass mat which onaverage is at least 1.33 times greater than the tensile strength of theglass mat substrate without the coating, wherein the coating comprises acoating blend which provides the coated glass mat with a porositysufficient to allow water vapor to escape from a gypsum slurry whenheated.
 2. The coated glass mat of claim 1, wherein the coating furthercomprises an inorganic binder.
 3. The coated glass mat of claim 1,wherein said non-woven glass mat weighs between about twelve pounds perthousand square feet and about fifty pounds per thousand square feet. 4.The coated glass mat of claim 1, wherein the glass mat substrate beforecoating weighs about fourteen and a half (14.5) pounds per thousandsquare feet and wherein after coating the coated glass mat has a tensilestrength which on average is greater than one hundred twenty pounds perthree-inch width.
 5. The coated glass mat of claim 1, wherein the glassmat substrate before coating weighs about twenty-six and a half (26.5)pounds per thousand square feet and wherein after coating the coatedglass mat has a tensile strength which on average is greater than twohundred twenty pounds per three-inch width.
 6. The coated glass mat ofclaim 1, wherein penetration of the coating into the glass mat substrateextends a depth of from twenty five percent of a thickness of the coatedglass mat to seventy five percent of the thickness of the coated glassmat.
 7. The coated glass mat of claim 1, wherein the coating uniformlypenetrates the glass mat substrate to a desired fractional thickness ofthe coated glass mat.